The pallet changing apparatus equips, as essential constituents, the pallet setup base which places a pallet, the table which places a workpiece with a state of before processing or after processed by means of the pallet, and the turning shaft which holds pallet changing arms extended on both sides and also turns along a horizontal direction together with the pallet changing arms.
The turning shaft equips a turning supporting portion which allows a ball bearing device, etc., to turn smoothly below a site which supports the pallet changing arm. In recent years, there is favorably adopted such a configuration that has a covering portion which covers from above a turning supporting portion in order to prevent chips generated due to cutting of workpieces by a main shaft from entering into the turning supporting portion.
On the other hand, for the sake of convenience of cutting work by the main shaft, the table often equips a rising portion which has an occillating center axis at a leading end of the table on the side of the turning shaft for allowing a region which places a workpiece by means of a pallet to oscillate freely and also equips an oscillating portion in which the region is supported by the turning shaft.
Where the table having the above-described rising portion moves back from and forth for a side of the turning shaft having the covering portion, the presence of the rising portion inevitably hinders the turning of the pallet changing arm.
Further, the fact that a certain space is occupied by the turning shaft firmly fixing the covering portion makes it worse since the above-mentioned is necessary for hindering problem.
In order to avoid the above-described problem, instead of the table which has the rising portion and moves back from and forth for a side of the turning shaft, there can be conceived such a configuration that, as shown in FIG. 5, a turning shaft 1 which firmly fixes a covering portion 2 is arranged at a side portion in a direction at which a table 4 which has an oscillating portion 41 and a rising portion 42 at the leading end side of the table moves back and forth, a pallet setup base 5 is arranged at a side portion further away from the table 4, and also the direction at which the table 4 moves back and forth is orthogonal to a direction at which the turning shaft 1 and the setup base 5 are arranged.
However, in the case of the configuration of the above-described arrangement, in addition to a space region in a direction at which the table 4 moves back and forth, a space region is also necessary at the side portion for changing a pallet. Thereby, it is impossible to achieve a compact pallet changing apparatus.
Where the configuration in which the table moves back from and forth for a side of the turning shaft is compared with the above-described configuration in which the constituents are arranged at the side portions, there is found such a relationship that the former configuration is larger in a region in which the table overlaps with the pallet changing arm in a vertical direction than the latter configuration. In the former configuration, it is possible to set the space necessary for turning of the pallet changing arm small.
Instead of the configuration in which the constituents are arranged at the side portions, where there is retained the configuration in which the table having the rising portion and the oscillating portion moves back from and forth for a side of the turning shaft, it is possible to conceive such a configuration that, on transfer of a pallet by using a table and a setup base, a turning shaft moves from an intermediate position between the table and the setup base to a position suitable for the transfer.
However, in the case of the above-described configuration, it is essential that not only the table moves back and forth but also the turning shaft moves. Therefore, complicated control becomes essential.
With regard to a pallet changing apparatus, various publicly-known technologies have been disclosed.
Of these publicly known technologies, in Patent Document 1, an oscillatory table 6 is moved by a table-driving device 30. However, a supporting shaft 42 which corresponds to the turning shaft is arranged at an oblique side portion in a direction at which the table 6 moves (FIGS. 1, 2, 4: the supporting shaft 42 is not provided with a covering portion).
However, as compared with the case of the orthogonal state shown in FIG. 5, the configuration of the above arrangement is such that a space region of the side portion necessary for changing a pallet is slightly smaller. This configuration is also unable to achieve a compact pallet changing apparatus.
In Patent Document 2, a turning member 34 which corresponds to the pallet changing arm is installed on a side of a table 6 which can oscillate along an oscillating axis 19 provided at a supporting portion 17 which corresponds to the rising portion, and also one of or both of the table 6 and a turning member 34 are allowed to move back and forth with each other (FIG. 2 and claim 1: the turning member 34 is not provided with a covering portion).
However, the above-described configuration is also similar to the configuration shown in FIG. 5 and the configuration described in Patent Document 1 in that it is unable to achieve a compact pallet changing apparatus.
Additionally, in the case of the above-described configuration, the table 6 is not only required to move back from and forth for a side of a lower region of the main shaft, but the turning member 34 and/or the table 6 are also required to move back and forth with each other in a direction different from the above-described back and forth movement. Therefore, complicated control is essential.
As described so far, although referring the publicly known technologies, proposal is not found for compact configuration of a pallet changing apparatus at all which supports a workpiece so as to oscillate by means of a pallet and which is provided with a rising portion having an oscillating center axis at the leading end of the turning shaft of the table which moves back from and forth for a side of the turning shaft and also covers from above a turning supporting portion at a lower end of the turning shaft.